Molecular organization of the COG vesicle tethering complex

Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA.
Nature Structural & Molecular Biology (Impact Factor: 13.31). 10/2010; 17(11):1292-7. DOI: 10.1038/nsmb.1917
Source: PubMed


Multisubunit tethering complexes of the CATCHR (complexes associated with tethering containing helical rods) family are proposed to mediate the initial contact between an intracellular trafficking vesicle and its membrane target. To begin elucidating the molecular architecture of one well-studied example, the conserved oligomeric Golgi (COG) complex, we reconstituted its essential subunits (Cog1, Cog2, Cog3 and Cog4) and used single-particle electron microscopy to reveal a y-shaped structure with three flexible, highly extended legs. Labeling experiments established that the N termini of all four subunits interact along the proximal segment of one leg, whereas three of the four C termini are located at the tips of the legs. Our results suggest that the central region of the Cog1-Cog2-Cog3-Cog4 complex, as well as the distal regions of at least two legs, all participate in interactions with other components of the intracellular trafficking machinery.

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    • "Cog8 seems to connect Cog1–4 with the Cog5–8 network, though it has not been possible to reconstitute the octameric complex (Fig. 4A and F). Lees at al. [116] mention that the human Cog2 sequence is significantly longer than its yeast homolog, and thus predict that the shape of human COG tetrameric complex is rather H-shaped. So far, detailed structural data of most parts are still missing, but shared homology on the ternary structural level could be found with exocyst. "
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    ABSTRACT: The HOPS multisubunit tethering factor (MTC) is a macromolecular protein complex composed of six different subunits. It is one of the key components in the perception and subsequent fusion of multivesicular bodies and vacuoles. Electron microscopy studies indicate structural flexibility of the purified HOPS complex. Inducing higher rigidity into HOPS by biochemically modifying the complex declines the potential to mediate SNARE-driven membrane fusion. Thus, we propose that integral flexibility seems to be not only a feature, but of essential need for the function of HOPS. This review focuses on the general features of membrane tethering and fusion. For this purpose, we compare the structure and mode of action of different tethering factors to highlight their common central features and mechanisms. Copyright © 2015. Published by Elsevier B.V.
    No preview · Article · Jun 2015 · FEBS letters
    • "Accordingly, malfunctions in the COG complex greatly impact on Golgi integrity, protein and lipid trafficking and glycosylation (Miller and Ungar, 2012; Ungar et al., 2006; Willett et al., 2013). The COG complex is organized into two functionally and structurally distinct sub-complexes, Lobe A (COG1–COG4) and Lobe B (COG5–COG8) (Laufman et al., 2011; Lees et al., 2010; Loh and Hong, 2004; Walter et al., 1998). Subunits of Lobe A are essential for growth in yeast. "
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    ABSTRACT: Searching and evaluating the Human Protein Atlas for transmembrane proteins enabled us to identify an integral membrane protein, TMEM115 that is enriched in the Golgi apparatus. Biochemical and cell biological analysis suggests that TMEM115 has 4 candidate transmembrane domains located at the N-terminal region. Both the N- and C-terminal domains are oriented towards the cytoplasm. Immunofluoresence analysis supports that TMEM115 is enriched in the Golgi cisternae. Functionally, TMEM115 knockdown or overexpression delays Brefeldin-A induced Golgi-to-ER retrograde transport, phenocopying cells with mutations or silencing of the COG complex. Co-immunoprecipitation and in vitro binding experiments reveals that TMEM115 interacts with COG complex, and may self-interact to form dimers or oligomers. A short region (residues 206-229) immediately to the C-terminal side of the 4(th) transmembrane domain is both necessary and sufficient for Golgi targeting. Knockdown of TMEM115 also reduces the binding of lectins PNA and HPA, suggesting an altered O-linked glycosylation profile. These results establish that TMEM115 is a novel integral membrane protein of the Golgi stack regulating Golgi-ER retrograde transport and is likely part of the machinery of the COG complex.
    No preview · Article · May 2014 · Journal of Cell Science
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    • "In the case of other complexes, only structures of fragments of individual subunits or subcomplexes are known. Recently, several tethering complexes including COG, TRAPPII and HOPS were isolated from native sources by affinity purification and analyzed by electron microscopy [11-13]. "
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    ABSTRACT: Biochemical and structural analysis of macromolecular protein assemblies remains challenging due to technical difficulties in recombinant expression, engineering and reconstitution of multisubunit complexes. Here we use a recently developed cell-free protein expression system based on the protozoan Leishmania tarentolae to produce in vitro all six subunits of the 600 kDa HOPS and CORVET membrane tethering complexes. We demonstrate that both subcomplexes and the entire HOPS complex can be reconstituted in vitro resulting in a comprehensive subunit interaction map. To our knowledge this is the largest eukaryotic protein complex in vitro reconstituted to date. Using the truncation and interaction analysis, we demonstrate that the complex is assembled through short hydrophobic sequences located in the C-terminus of the individual Vps subunits. Based on this data we propose a model of the HOPS and CORVET complex assembly that reconciles the available biochemical and structural data.
    Full-text · Article · Dec 2013 · PLoS ONE
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